This invention relates to special effects video devices such as character generators used in television studios and broadcast facilities to generate video signals that represent alpha numeric characters and other symbols to be presented in a television display. It is an object in design of symbol generators to be able to provide symbols that are more complex than simple letters and numbers, and to be able to change the positions and colors of symbols and otherwise manipulate symbols in a display to create special effects. To achieve these objectives a symbol generator must generate and modify video signal information or a video signal very quickly.
The popular design approach of current symbol generators utilizes frame buffers to manipulate symbols or update video signals. Frame buffers include separate storage locations for recording data pertaining to each separate display location of a television display screen or raster. The frame buffer design requires that a very large amount of data be processed to provide and update video signals. Frame buffer systems achieve animation by moving blocks of data representing portions of a video image to be modified, formulating vectors, and filling memory blocks of the frame buffers with desired display patterns. Complex electronics are required to identify the portion of a display to be modified and manipulate blocks within a frame buffer representing those portions of the image.
There have been prior efforts to design a pipeline system that would regenerate a complete video signal representing all portions of an image each field and thereby avoid the requirement of frame buffer systems to identify particular portions of a video signal or blocks of data to be modified from one field to the next. The prior efforts have included use of symbol boundaries to reduce the amount of data from that which must be processed in a frame buffer system. They have not been successful and have not resulted in a practical commercial product. The capabilities of both frame buffer and prior pipeline designs has been limited with respect to dynamic display characteristics, the speed at which video signal data is handled, the amount of data that is required to be processed, the extent of special effects that can be provided, symbol movement, and the avoidance of distortion in the output images.